1. Field of the Invention
The present invention relates to a device which is provided in an electronic still video camera, for example, and which electronically develops an image on a recording medium, and reads the image from the recording medium.
2. Description of the Related Art
Conventionally, silver halide photographic material is generally used as a material for recording an optical image. Silver halide photographic material has high optical sensitivity and high resolution, and the economical efficiency thereof is excellent. However, silver halide photographic material has drawbacks in that not only is the developing process cumbersome but also a visible image cannot be obtained at the same time as photography. A dry-type developing method has been developed to simplify the developing process. However, simultaneous development in which a visible image is obtained upon photography is impossible in the dry-type developing method.
On the other hand, as non-silver-halide photographic materials, there are known electrophotographic materials, diazotype photographic materials and free-radical photographic materials and so on. In these materials, however, there is no material which has advantageous characteristics like silver halide photographic material, while being able to simultaneously develop and keep a visible image. Note that, electrophotographic materials have been used mainly in copying machines, since they can perform dry-type development and can simultaneously develop an electrostatic latent image, which is obtained by exposure, using toner.
In such electrophotographic materials, recently, a photographic material has been developed in which a recording material made of the photographic material is electronically and directly developed similarly to a silver halide photographic material, so that the developed visible image can be immediately seen or recorded. Such a recording material in which a visible image is electronically developed is referred to as an electro-developing recording material in this specification.
Japanese Unexamined Patent Publication No. 5-2280 and U.S. Pat. No. 5,424,156, for example, discloses a recording material which is a combination of an electrostatic information recording material and an electric charge keeping medium, the electrostatic information recording material having a photoconducting layer and an inorganic oxide material layer, and the electric charge keeping medium having a liquid crystal display. In this structure, when the electrostatic information recording material is exposed while an electric voltage is applied to the electrostatic information recording material and the electric charge keeping medium, electric charge in accordance with the amount of incident light is generated in the electrostatic information recording material. Since the intensity of electric field applied to the liquid crystal display facing the electrostatic information recording material is varied in accordance with the generated electric charge, an image corresponding to the amount of light distribution is indicated or developed on the liquid crystal display.
The image kept by the electro-developing recording medium may be read out through an optical sensor, and a light source may be provided to illuminate the electro-developing recording medium so that the optical sensor can read the image. In such a construction, however, if the light distribution characteristics of the light source are not uniform along the optical sensor, the image cannot be exactly read out by the optical sensor. Therefore, the image signal, which is generated by the optical sensor in accordance with the image, should be subjected to a correction process, which is complicated, so that the effect of the light distribution characteristics is reduced. Therefore, a time for which the correction process is performed is long.
If the optical sensor is a line sensor, the line sensor is intermittently moved along the electro-developing recording medium, and thus a reading operation, in which a part of the image is read by the line sensor, and a discharging operation, in which residual electric charge is discharged from the line sensor, are alternately carried out. Therefore, it takes a long time to read the image from the electro-developing recording medium.
Further, the device, in which the light source and the optical sensor are provided around the electro-developing recording medium, is bulky, and thus there is a limit in miniturizing the device.
On the other hand, a plurality of primary color images can be formed on the electro-developing recording medium through a dichroic optical member, and the color images can be read out through a single line sensor by scanning the line sensor along the electro-developing recording medium. In such a construction, however, a large storage memory must be provided for temporarily storing each of the color images. As a result, the time for the scanning operation takes too long.
In the device having the large storage memory, in a state in which the image developed by the electro-developing recording medium is not read out therefrom, the large storage memory is not used. Namely, the working ratio of the large storage memory is not high.